What the ASVAB is testing
Inclined plane and hydraulics questions both test one core concept: force multiplication through geometry. The ASVAB presents a ramp, a wedge, a screw, or a hydraulic cylinder and asks you to calculate output force or mechanical advantage. The numbers are always clean — no guessing required if you use the right formula.
Inclined planes: the long-cut principle
A ramp reduces the effort needed to raise a load by spreading the work over a longer distance. The steeper the ramp, the closer it is to lifting straight up — MA approaches 1 and you gain nothing. The shallower the ramp, the easier the push — but the longer you have to push.
MA = ramp length ÷ ramp height
A ramp 10 feet long rising 2 feet has MA = 5. You push one-fifth the load's weight, but you push it 10 feet for a 2-foot rise.
Wedge: Two inclined planes back-to-back. An axe splitting wood, a door stop, a zipper tooth — all wedges. MA = slant length ÷ width at the thick end. Longer and thinner = higher MA.
Screw: An inclined plane wrapped into a helix. One turn of the screw advances the fastener one pitch. Fine-thread screws (more turns per inch) have higher MA and greater holding power; coarse threads advance faster.
Hydraulics: Pascal's law in practice
A hydraulic system uses an incompressible fluid to transmit force. When you push on a small piston, pressure (force per unit area) spreads equally throughout the fluid. That same pressure acts on a larger output piston, producing a proportionally larger force.
P = F₁ ÷ A₁ = F₂ ÷ A₂
Rearranged: F₂ = F₁ × (A₂ ÷ A₁)
A 10:1 area ratio gives 10:1 force multiplication. The catch: the input piston must travel 10 times as far as the output piston moves. Work in = work out (ideal system, no losses).
Real-world examples: automotive brake systems, hydraulic jacks, power-steering systems, construction equipment lifts.
The common trap on both topics
Both inclined planes and hydraulics require computing an area or length ratio before finding force. The most common mistake is plugging in the wrong dimension — using diameter instead of area for a piston, or height instead of ramp length for MA. Stop, identify what the question is giving you, convert if needed, then calculate.